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[phys.org] Semi-transparent perovskite solar cells for solar windows

1K views 19 replies 11 participants last post by  superstition222 
#1 ·
Quote:
Scientists are exploring ways to develop transparent or semi-transparent solar cells as a substitute for glass walls in modern buildings with the aim of harnessing solar energy. But this has proven challenging, because transparency in solar cells reduces their efficiency in absorbing the sunlight they need to generate electricity.
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Using perovskites, a Korean research team, led by Professor Seunghyup Yoo of the Korea Advanced Institute of Science and Technology and Professor Nam-Gyu Park of Sungkyunkwan University, has developed a semi-transparent solar cell that is highly efficient and functions very effectively as a thermal mirror.


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The semi-transparent solar cells made with the TTEs exhibited an average power conversion efficiency as high as 13.3%, reflecting 85.5% of incoming infrared light. Currently available crystalline silicon solar cells have up to 25% efficiency but are opaque.
SOURCE

Self-powered sun HUDs anyone?
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#2 ·
Sounds about as useful as wicker washbasin.
 
#4 ·
Quote:
Originally Posted by Zero4549 View Post

Sounds about as useful as wicker washbasin.
Mind explaining that backward stance?

This is perfect for commercial building construction. One of the biggest expenditures is AC due to solar heating of the building, and one of the major ways of making a building more appealing is reducing the thermal load by infrared-reflective paneling on the windows. This is already a market.

The idea that you can take something you're already paying for as part of commercial building construction and instead use it to further reduce your electric bill is astoundingly useful.

So, how again is this useless?
 
#8 ·
I wonder if these solar cells could be placed on top of a tint like from Huper Optik that reflects 98% of IR and 99.9% UV. That way the solar cells use the IR heat that is coming towards a window as best they can, reflect some of it away, and the stuff that gets through a good portion would be reflected right back out, passing through the cell once again, providing more heat usage and rejection at the same time.
 
#9 ·
Quote:
Originally Posted by EniGma1987 View Post

I wonder if these solar cells could be placed on top of a tint like from Huper Optik that reflects 98% of IR and 99.9% UV. That way the solar cells use the IR heat that is coming towards a window as best they can, reflect some of it away, and the stuff that gets through a good portion would be reflected right back out, passing through the cell once again, providing more heat usage and rejection at the same time.
Only a small amount of IR is useful for a solar cell. It does help, and in fact there are more photons in the near infrared than there are in the visible, but the absorption band for silicon cuts off at around 1.1 microns. Anything longer wavelength can't get turned into electricity by the solar cell. Perovskites seem to be able to be designed to push the edge of their absorption band a little farther than what you get with silicon, but it won't be much farther. The bulk of the heating, though, is MUCH longer wavelength. That's the stuff you still need to reflect, but doesn't help if it does a double-pass through the solar cell.

But yes, if you made a low-reflectance solar cell, and had a higher reflectance layer underneath it, you'd get improved solar cell performance. It's only really applicable with these semi-transparent cells, as with other materials they're rather opaque and putting a reflector underneath won't help because there's nothing to reflect.
 
#10 ·
It seems quite possible that in a more "symbiotic" arrangement, a silicon cell could be tuned to clean up what this misses and stacked with it. So then you've got ≅ 13.3+25 nearly 40% conversion.

Of course "seems" denotes my limited external viewpoint.
 
#11 ·
As an architect by trade, I don't like the color (maybe because I am refurbishing a bronze colored glass tower build in the 80s in Pasadena CA as we speak...), but there are definitely applications for this technology.

Yes there are other coating technologies for glazing envelopes, but nothing stops you from using this sandwiched with other coatings and films...the only issue is that the solar cell needs to be in-front of all of the above, so the color will be that bronze ( assuming the picture linked is roughly true to life) which I personally would not choose. Overall the glass that carries the cell will probably need to be the outer part of a IGU (insulated glass unit) if it was to replace glazing inside a window.

So, some long wave radiation will creep into the mass of the glass and then radiate inside the room regardless of the type of glass or coatings. So in reality PV systems are working counter to what glaze coatings / films should be doing: PVs want the radiation to permeate in their mass to create current. Coatings want to reflect as much of the radiation back, because once it makes its way into the glazing, it is practically inside the building...there is just a time lag between the glass receiving the heat and radiating it back inside the room.

Thus the best application for this technology would be in creating a second layer of envelope, i.e. a 2-skin facade where the exterior portion "shades" the inner one, with the inner one providing the weather sealing. These applications are super expensive and developers avoid them as those rarely pencil out for a simple payback within the lifetime of the cell (i.e. the PV / shading system needs to generate more savings than its cost over the expected lifetime, typ. 15y for a PV system before it needs at least partial replacement).
 
#14 ·
Quote:
Originally Posted by Zero4549 View Post

Sounds about as useful as wicker washbasin.
headscratch.gif


Quote:
Originally Posted by Mand12 View Post

Mind explaining that backward stance? This is perfect for commercial building construction. One of the biggest expenditures is AC due to solar heating of the building, and one of the major ways of making a building more appealing is reducing the thermal load by infrared-reflective paneling on the windows. This is already a market.

The idea that you can take something you're already paying for as part of commercial building construction and instead use it to further reduce your electric bill is astoundingly useful.

So, how again is this useless?
Said it a Hell of a lot better than I.
 
#15 ·
Quote:
Originally Posted by Mand12 View Post

Mind explaining that backward stance?

This is perfect for commercial building construction. One of the biggest expenditures is AC due to solar heating of the building, and one of the major ways of making a building more appealing is reducing the thermal load by infrared-reflective paneling on the windows. This is already a market.

The idea that you can take something you're already paying for as part of commercial building construction and instead use it to further reduce your electric bill is astoundingly useful.

So, how again is this useless?
The problem with Solar Panels that don't move with the arch of the sun is that they are extremely inefficient in practice. There may be certain applications that would be perfect for solar windows, but similar to solar roadways, in practice, it will have many issues unless it's priced competitively with existing solar panels which are probably more efficient already.

I do like the idea of putting these into electric vehicles on premium trims, it would probably only get you a mile or two a day (if weather is ideal), but still, it's pretty cool.

The idea that this will replace already-existing 'thermal windows' anytime soon is entirely baseless unless you think a triple-pane or quadruple-pane window will cost the same as a semi-transparent solar cell. One day it might be worth it, probably not in the next 10 years.
 
#16 ·
Quote:
Originally Posted by un-midas touch View Post

It seems quite possible that in a more "symbiotic" arrangement, a silicon cell could be tuned to clean up what this misses and stacked with it. So then you've got ≅ 13.3+25 nearly 40% conversion.

Of course "seems" denotes my limited external viewpoint.
You then don't get to be able to look out of your windows.

There are plenty of ways of improving solar cells. The point of this one is that it's a solar cell that still has enough transmission to function as a building window.
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Originally Posted by Dotachin View Post

Wouldn't that reduce the light coming into the building? Because that is the whole point of the window: let light in.
For residential windows, yes, more light is generally good. For commercial windows, it's not even close. Typical commercial windows are in the 20% transmission range, and they do that so the people inside, with relatively weak indoor lighting, can still see the bright, bright outside world through the mostly-reflective window coating. Outside of the visible, they try to get as high a reflectance as possible.

You could have a completely transparent window in your commercial building like you might expect to have at home, but then the AC costs for the building become enormous. You *need* to keep that light out in order to be remotely energy-efficient, which in this case translates directly to overhead operating costs. While your employees might like a bit more natural light inside, the tradeoff for a large office building or similar simply isn't economically feasible.
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Originally Posted by Buris View Post

The problem with Solar Panels that don't move with the arch of the sun is that they are extremely inefficient in practice. There may be certain applications that would be perfect for solar windows, but similar to solar roadways, in practice, it will have many issues unless it's priced competitively with existing solar panels which are probably more efficient already.
Again, these aren't competing with dedicated solar panels for energy production. They're competing with windows, and they generate way more electricity than those.

Also, lack of sun tracking does not make panels "extremely inefficient in practice." Yes, you get a cosine falloff, but that's not enough to make them impractical. Hell, I live in the northeast US, and even at that relatively high latitude for the United States, and even with significantly more overcast days than in a place like Arizona where I grew up and where there are fully-functional solar power plants, there are still a ton of static-mounted solar panels on roofs that provide plenty enough power to make most houses net zero electricity consumption. You do take an efficiency loss, but that doesn't make it impractical.
Quote:
Originally Posted by Buris View Post

The idea that this will replace already-existing 'thermal windows' anytime soon is entirely baseless unless you think a triple-pane or quadruple-pane window will cost the same as a semi-transparent solar cell. One day it might be worth it, probably not in the next 10 years.
You will still need triple/quad-pane windows for thermal insulation. What this is competing with is the reflective film they put on the windows, and yes, that film is currently very cheap. But, you have to invent a thing before you make it economical, and the news of this is the invention. Not really warranted to poke holes at how it isn't market-competitive when it didn't exist before these people made it work at all. It will get there, as the cost of installation drops and the cost of electricity grows.
 
#17 ·
@Mand12 Went though a lot and I mostly agree.

Quote:
Originally Posted by Dotachin View Post

Wouldn't that reduce the light coming into the building? Because that is the whole point of the window: let light in.
As said by the above user, for residential applications where you have a few windows, at best 20-30% of your wall area being glazed, it might be an issue, but 20% "darker" windows are not that much of a deal, People do far darker tints in their cars all the time.
Especially in south and predominantly SE or SW facing orientations in areas with lots of sunny days, you will most actually like it as it will decrease the contrast between indoor and outdoor lighting. North facing vertical surfaces receive no direct radiation from the sun (in the North Hemisphere) so you would not place PV "anything" there.

In commercial buildings (think glass towers for simplicity), you often get north of 80% of wall area being glazed, at least in the areas next to the facade of the building. This often means "too much" light and even more often, too much heat. Cutting the % of radiation that actually makes it into the building, both as light and as heat is actually super desired. Modern glass buildings often have automated blinds that linked to light sensors adjust and shade the windows, otherwise achieving a balanced lighting throughout the space is nearly impossible, or it becomes a big waste putting in artificial lights that can do this balancing act - with a huge bill in both installation and running costs.


As you see above, balancing the $ you spend on lighting goes a long way: office buildings spend the largest % of their electric bill on lighting, more than cooling, and that is often happening because we go for "too much" light overall, something that especially today where most are working with self-illuminated screens is a huge waste.
Quote:
Originally Posted by Buris View Post

The problem with Solar Panels that don't move with the arch of the sun is that they are extremely inefficient in practice. There may be certain applications that would be perfect for solar windows, but similar to solar roadways, in practice, it will have many issues unless it's priced competitively with existing solar panels which are probably more efficient already.
Most high rise buildings have much less roof area than south / roughly south facing facade area. Even mid-rise buildings might have roughly equal the above two. So it makes sense tapping into the possibility of using your facade ONTOP of your roof with more traditional / more efficient panels.

And solar tracking is not a real game changer, it adds perhaps 20-25% of efficiency over a fixed system, and that in areas with very high solar irradiance values - i.e. California, Arizona etc, makes sense looking at least into a single axis tracking system, when you are limited in area. Otherwise if you have the area to play with - perhaps not on the roof but on the combined roof + facade area, it is almost always better to add 25% more fixed panels than introducing a more complex system that adds cost and perhaps complicates maintenance. Note that solar tracking mechanisms rarely have more than 5y warranties (typ 2, rarely 10), while panels often go as high as 15y and lately 25y. Makes a big difference if you have to replace something twice as often (not a guaranteed failure, but will happen when you don't deploy just a handful of them...do 100s of panels, and the solid-state nature of the PVs themselves has you covered...but 100s of trackers? Yeah, a % will have issue really soon...

Just like with a HDD bank...individuals live "forever", get a data-center sized sample and monitor them over a few years, and you can see em dying reliably and repeatedly.

There are "passive" solar trackers that are more reliable but also less responsive, and there are simple adjustments, like manually adjusting the panel's tilt for every season, that also get you increased efficiency...if you are not talking on a residential scale, or if you are talking off-grid applications, everything matters, but it is subject to a cost/benefit analysis. You should not assume that tracking systems are better.
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Originally Posted by maltamonk View Post

Is there a reason for the copper color? I could definitely see something like this in EV used as sun/moon roofs
The silica or whatever material crystals they are using have a set chemistry / molecular structure that leads to this coloration. It is not an option, just like the Crystalline silicon (c-Si) they use in most opaque PVs is that blue-ish color.



It is not chosen to be copper / bronze color, it might be the "only coloration possible" at this moment.
 
#18 ·
Perovskite tech is exciting because it's cheap to make. It can be sprayed on and involves chemical reactions under easy conditions, rather than high temperatures for silicon.

It also doesn't involve expensive elements like tellurium and indium - or the silver used in monocrystalline silicon cells.

It doesn't involve flurocarbons like silicon production.

But, perovskites have two major hurdles:

1) stability under environmental conditions (rather than degradation)

2) either replacing lead with something else that's non-toxic, like tin, or restricting lead-based perovskites to usage where the layer is totally protected and where mandatory recycling is required

There is also the minor hurdle of replacing toxic chemicals needed as part of the manufacturing process with less toxic alternatives. This research has been underway and some progress has been made.

Perovskites can, indeed, be layered on top of other types of solar cells to increase efficiency. However, another massive utility is their cheapness and spray-on easy - both of which can make quantity of surface area covered outweigh the lack of per square cm efficiency.

Issues with the stability of iodides may make perovskite never acceptable for mass-market products. Research is still ongoing into this problem.
 
#19 ·
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Originally Posted by superstition222 View Post

Perovskites can, indeed, be layered on top of other types of solar cells to increase efficiency. However, another massive utility is their cheapness and spray-on easy - both of which can make quantity of surface area covered outweigh the lack of per square cm efficiency.
Well lemme ask you. do you get more energy collection if you spray on more coats at the cost of transparency? Or is the 13.3% basically all it gives?
 
#20 ·
Quote:
Originally Posted by un-midas touch View Post

Well lemme ask you. do you get more energy collection if you spray on more coats at the cost of transparency? Or is the 13.3% basically all it gives?
I wouldn't worry about the efficiency rate right now. The bigger problem is making perovskites stable enough to be used for commercial products. If, and when, that happens then efficiency will likely have increased. The main reason perovskite is exciting to people is how cheap it is to make.

Perovskite tech can yield more efficiency than 13.3% now, but I don't know about the effect of spray thickness. A tandem perovskite cell was recently made in Toledo Ohio that has an 18% efficiency. A Korean university says it has reached 21.3% with perovskite.
 
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